Tire Size Box

325/25R22 vs 315/30R22

315/30R22 compared with 325/25R22

+3.7% diameter, −0.4" width

315/30R22 is 29.44" tall vs 28.40". More than the 3% rule of thumb, so check carefully before switching.

28.4"22" rim3.2"12.8" wide
325/25R22 (solid) compared with 315/30R22 (dashed outline), drawn to scale

With 315/30R22 tires, when your speedometer says 60 mph you are really going

62.2 mph

315/30R22 is +1.04 inches (+3.7%) in overall diameter. That is more than the 3% most shops and makers recommend.

325/25R22315/30R22Difference%
Overall diameter28.40"29.44"+1.04"+3.7%
Section width12.80"12.40"−0.39"−3.1%
Sidewall height3.20"3.72"+0.52"+16.3%
Circumference89.21"92.49"+3.28"+3.7%
Revolutions per mile710.2685.0−25.2−3.5%

Speedometer difference

If your vehicle came with 325/25R22 and you fit 315/30R22, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.7 mph+0.7 mph
30 mph31.1 mph+1.1 mph
40 mph41.5 mph+1.5 mph
50 mph51.8 mph+1.8 mph
60 mph62.2 mph+2.2 mph
65 mph67.4 mph+2.4 mph
70 mph72.6 mph+2.6 mph
75 mph77.8 mph+2.8 mph
80 mph82.9 mph+2.9 mph

Each size on its own

Questions

Which is bigger, 325/25R22 or 315/30R22?
315/30R22 is taller by 1.04 inches (29.44" vs 28.40"). 325/25R22 is wider by 0.39 inches.
Can I replace 325/25R22 with 315/30R22?
It is not recommended without checking carefully. The diameter difference is +3.7%, more than the 3% most shops and makers allow. It will throw off the speedometer and may affect ABS, stability control and clearance.
How much will 315/30R22 change my speedometer?
When your speedometer reads 60 mph with 315/30R22 fitted (calibrated for 325/25R22), your real speed is 62.2 mph. Your odometer will under-count miles by about 3.7%.
Will 315/30R22 lift my vehicle?
Ride height changes by half the diameter difference: +0.52 inches of ground clearance at the axle.

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